bims-microg 2024-09-22 papers

bims-microg

Biomed News

on Microglia in health and disease

Issue of 2024–09–22
33 papers selected by
Marcus Karlstetter, Universität zu Köln

Ready-to-use iPSC-derived microglia progenitors for the treatment of CNS disease in mouse models of neuropathic mucopolysaccharidoses.
Transcription factor EGR2 alleviates autoimmune uveitis via activation of GDF15 to modulate the retinal microglial phenotype.
Transcriptional profiling in microglia across physiological and pathological states identifies a transcriptional module associated with neurodegeneration.
A human Tau expressing zebrafish model of progressive supranuclear palsy identifies Brd4 as a regulator of microglial synaptic elimination.
Lipid-laden macrophages recycle myelin to feed glioblastoma.
Microglial and neuronal fates following inhibition of CSF-1R in synucleinopathy mouse model.
A comprehensive review of AAV-mediated strategies targeting microglia for therapeutic intervention of neurodegenerative diseases.
SMAC mimetic drives microglia phenotype and glioblastoma immune microenvironment.
Trem2-deficiency aggravates and accelerates age-related myelin degeneration.
Microglia mediate memory dysfunction via excitatory synaptic elimination in a fracture surgery mouse model.
The regulation of NFKB1 on CD200R1 expression and their potential roles in Parkinson's disease.
Microglial morphology aligns with vigilance stage-specific neuronal oscillations in a brain region-dependent manner.
Microglia in physiological conditions and the importance of understanding their homeostatic functions in the arcuate nucleus.
Hematopoietic stem cell gene therapy to halt neurodegeneration.
Microglia and macrophages alterations in the CNS during acute SIV infection: A single-cell analysis in rhesus macaques.
Striking and widespread microglial activation in the brains of Southdown lambs with type II glucocerebrosidosis (neuronopathic Gaucher disease).
Lactobacilli Cell-Free Supernatants Modulate Inflammation and Oxidative Stress in Human Microglia via NRF2-SOD1 Signaling.
Lipid metabolic rewiring in glioma‑associated microglia/macrophages (Review).
Knockout of TNF-α in microglia decreases ferroptosis and convert microglia phenotype after spinal cord injury.
Rhodium nanozyme mitigates RPE degeneration and preserves vision in age-related macular degeneration via antioxidant and anti-inflammatory mechanisms.
Propofol alleviates M1 polarization and neuroinflammation of microglia in a subarachnoid hemorrhage model in vitro, by targeting the miR-140-5p/TREM-1/NF-κB signaling axis.
Gas6/Axl signaling promotes hematoma resolution and motivates protective microglial responses after intracerebral hemorrhage in mice.
Bulk and single-cell RNA-seq analyses reveals canonical RNA editing associated with microglial homeostasis and its role in sepsis-associated encephalopathy.
AB046. Dual role of POSTN in maintaining glioblastoma stem cells and immune-suppressive microglia in glioblastoma.
Simple and highly specific targeting of resident microglia with adeno-associated virus.
Galantamine and wedelolactone combined treatment suppresses LPS-induced NLRP3 inflammasome activation in microglial cells.
Phillygenin attenuates cell apoptosis and microglia activation in cerebral ischaemia-reperfusion rats through activation of peroxisome proliferator-activated receptor γ.
Krebs cycle derivatives, dimethyl fumarate and itaconate, control metabolic reprogramming in inflammatory human microglia cell line.
Cannabinoid type 2 receptor deficiency leads to Aβ-induced cognitive impairment through promoting microglial sensitivity to Aβ in the prefrontal cortex in mice.
HSV-1 immune escapes in microglia by down-regulating GM130 to inhibit TLR3-mediated innate immune responses.
Nrf2 Deficiency Exacerbates Parkinson's Disease by Aggravating NLRP3 Inflammasome Activation in MPTP-Induced Mouse Models and LPS-Induced BV2 Cells.
P2Y12-targeted modulation of microglial phenotypes: A novel therapeutic strategy for enhanced axonal regeneration post-spinal cord injury.
Constitutive expression of the deubiquitinating enzyme CYLD does not affect microglia phenotype or function in homeostasis and neuroinflammation.

Nat Commun. 2024 Sep 16. 15(1): 8132

Ready-to-use iPSC-derived microglia progenitors for the treatment of CNS disease in mouse models of neuropathic mucopolysaccharidoses.

Panagiotis Douvaras, Diego F Buenaventura, Bruce Sun, Ashley Lepack, Elizabeth Baker, Elizabeth Simpson, Mark Ebel, Gregory Lallos, Deven LoSchiavo, Nicholas Stitt, Nathaniel Adams, Conor McAuliffe, Ana Forton-Juarez, Brian Kosmyna, Elizabeth Pereira, Benjamin Burnett, David Dilworth, Stephanie Fisher, Jing Wang, Peter Tonge, Mark Tomishima, Carlos Paladini, Dan Wilkinson, Chew-Li Soh, Maya Srinivas, Christoph Patsch, Stefan Irion.

Mucopolysaccharidoses are inherited metabolic disorders caused by the deficiency in lysosomal enzymes required to break down glycosaminoglycans. Accumulation of glycosaminoglycans leads to progressive, systemic degenerative disease. The central nervous system is particularly affected, resulting in developmental delays, neurological regression, and early mortality. Current treatments fail to adequately address neurological defects. Here we explore the potential of human induced pluripotent stem cell (hiPSC)-derived microglia progenitors as a one-time, allogeneic off-the-shelf cell therapy for several mucopolysaccharidoses (MPS). We show that hiPSC-derived microglia progenitors, possessing normal levels of lysosomal enzymes, can deliver functional enzymes into four subtypes of MPS knockout cell lines through mannose-6-phosphate receptor-mediated endocytosis in vitro. Additionally, our findings indicate that a single administration of hiPSC-derived microglia progenitors can reduce toxic glycosaminoglycan accumulation and prevent behavioral deficits in two different animal models of MPS. Durable efficacy is observed for eight months after transplantation. These results suggest a potential avenue for treating MPS with hiPSC-derived microglia progenitors.

DOI: https://doi.org/10.1038/s41467-024-52400-8
Proc Natl Acad Sci U S A. 2024 Sep 24. 121(39): e2316161121

Transcription factor EGR2 alleviates autoimmune uveitis via activation of GDF15 to modulate the retinal microglial phenotype.

Wanqian Li, Siyuan He, Jun Tan, Na Li, Chenyang Zhao, Xiaotang Wang, Zhi Zhang, Jiangyi Liu, Jiaxing Huang, Xingran Li, Qian Zhou, Ke Hu, Peizeng Yang, Shengping Hou.

  Uveitis is a vision-threatening disease primarily driven by a dysregulated immune response, with retinal microglia playing a pivotal role in its progression. Although the transcription factor EGR2 is known to be closely associated with uveitis, including Vogt-Koyanagi-Harada disease and Behcet's disease, and is essential for maintaining the dynamic homeostasis of autoimmunity, its exact role in uveitis remains unclear. In this study, diminished EGR2 expression was observed in both retinal microglia from experimental autoimmune uveitis (EAU) mice and inflammation-induced human microglia cell line (HMC3). We constructed a mice model with conditional knockout of EGR2 in microglia and found that EGR2 deficiency resulted in increased intraocular inflammation. Meanwhile, EGR2 overexpression downregulated the expression of inflammatory cytokines as well as cell migration and proliferation in HMC3 cells. Next, RNA sequencing and ChIP-PCR results indicated that EGR2 directly bound to its downstream target growth differentiation factor 15 (GDF15) and further regulated GDF15 transcription. Furthermore, intravitreal injection of GDF15 recombinant protein was shown to ameliorate EAU progression in vivo. Meanwhile, knockdown of GDF15 reversed the phenotype of EGR2 overexpression-induced microglial inflammation in vitro. In summary, this study highlighted the protective role of the transcription factor EGR2 in AU by modulating the microglial phenotype. GFD15 was identified as a downstream target of EGR2, providing a unique target for uveitis treatment.

Keywords:  EGR2; GDF15; autoimmune uveitis; microglia

DOI:  https://doi.org/10.1073/pnas.2316161121
Commun Biol. 2024 Sep 18. 7(1): 1168

Transcriptional profiling in microglia across physiological and pathological states identifies a transcriptional module associated with neurodegeneration.

Aysegul Guvenek, Neelroop Parikshak, Daria Zamolodchikov, Sahar Gelfman, Arden Moscati, Lee Dobbyn, Eli Stahl, Alan Shuldiner, Giovanni Coppola.

Microglia are the resident immune cells of the central nervous system and are involved in brain development, homeostasis, and disease. New imaging and genomics technologies are revealing microglial complexity across developmental and functional states, brain regions, and diseases. We curated a set of publicly available gene expression datasets from human microglia spanning disease and health to identify sets of genes reflecting physiological and pathological microglial states. We also integrated multiple human microglial single-cell RNA-seq datasets in Alzheimer's disease (AD), multiple sclerosis (MS), and Parkinson's disease, and identified a distinct microglial transcriptional signature shared across diseases. Analysis of germ-line DNA identified genes with variants associated with AD and MS that are overrepresented in microglial gene sets, including the disease-associated transcriptional signature. This work points to genes that are dysregulated in disease states and provides a resource for the analysis of diseases in which microglia are implicated by genetic evidence.

DOI: https://doi.org/10.1038/s42003-024-06684-7
Nat Commun. 2024 Sep 18. 15(1): 8195

A human Tau expressing zebrafish model of progressive supranuclear palsy identifies Brd4 as a regulator of microglial synaptic elimination.

Qing Bai, Enhua Shao, Denglei Ma, Binxuan Jiao, Seth D Scheetz, Karen A Hartnett-Scott, Vladimir A Ilin, Elias Aizenman, Julia Kofler, Edward A Burton.

Progressive supranuclear palsy (PSP) is an incurable neurodegenerative disease characterized by 4-repeat (0N/4R)-Tau protein accumulation in CNS neurons. We generated transgenic zebrafish expressing human 0N/4R-Tau to investigate PSP pathophysiology. Tau zebrafish replicated multiple features of PSP, including: decreased survival; hypokinesia; impaired optokinetic responses; neurodegeneration; neuroinflammation; synapse loss; and Tau hyperphosphorylation, misfolding, mislocalization, insolubility, truncation, and oligomerization. Using automated assays, we screened 147 small molecules for activity in rescuing neurological deficits in Tau zebrafish. (+)JQ1, a bromodomain inhibitor, improved hypokinesia, survival, microgliosis, and brain synapse elimination. A heterozygous brd4+/- mutant reducing expression of the bromodomain protein Brd4 similarly rescued these phenotypes. Microglial phagocytosis of synaptic material was decreased by (+)JQ1 in both Tau zebrafish and rat primary cortical cultures. Microglia in human PSP brains expressed Brd4. Our findings implicate Brd4 as a regulator of microglial synaptic elimination in tauopathy and provide an unbiased approach for identifying mechanisms and therapeutic targets in PSP.

DOI: https://doi.org/10.1038/s41467-024-52173-0
Cancer Res. 2024 Sep 18.

Lipid-laden macrophages recycle myelin to feed glioblastoma.

Lizhi Pang, Fei Zhou, Peiwen Chen.

Tumor-associated microglia and macrophages (TAMs) make up the largest immune cell population in the glioblastoma (GBM) tumor microenvironment (TME). Given the heterogeneity and plasticity of TAMs in the GBM TME, understanding the context-dependent cancer cell-TAM symbiotic interaction is crucial for understanding GBM biology and developing effective therapies. In a recent issue of Cell, Kloosterman and colleagues identified a subpopulation of GPNMBhigh lipid-laden microglia and macrophages (LLMs) in GBM. Mesenchymal-like (MES-like) GBM cells help to generate the LLM phenotype. Reciprocally, LLMs are epigenetically rewired to recycle myelin and transfer the lipid from myelin to cancer cells, fueling MES-like GBM progression in an LXR/ABCA1-dependent manner. Together, leveraging LLMs opens new therapeutic possibilities for rewiring the metabolism-mediated tumor-TAM interaction during GBM progression.

DOI: https://doi.org/10.1158/0008-5472.CAN-24-3362
Brain Behav Immun. 2024 Sep 14. pii: S0889-1591(24)00619-6. [Epub ahead of print]

Microglial and neuronal fates following inhibition of CSF-1R in synucleinopathy mouse model.

Michiyo Iba, Yeon-Joo Lee, Liam Horan-Portelance, Katherine Chang, Marcell Szabo, Robert A Rissman, Sungyong You, Eliezer Masliah, Changyoun Kim.

Synucleinopathies are age-related neurological disorders characterized by the abnormal accumulation of α-synuclein (α-syn) in neuronal and non-neuronal cells. It has been proposed that microglial cells play an important role in synucleinopathy neuroinflammation, as well as homeostatically, such as in the clearance of α-syn aggregates in the brain. Here, we examined the effects of microglia on the pathogenesis of synucleinopathies by cell depletion in a mouse model of synucleinopathies. For this purpose, we treated non-transgenic (Non-tg) and α-synuclein transgenic (α-syn-tg) mice with pexidartinib (PLX3397), a tyrosine kinase inhibitor of colony-stimulating factor 1 receptor (CSF-1R). Neuropathological and immunoblot analysis confirmed that Iba-1 immunoreactive microglial cells were decreased by 95% following PLX3397 treatment in Non-tg and α-syn-tg mice. The level of total α-syn in the Triton X-insoluble fraction of brain homogenate was significantly decreased by microglial depletion in the α-syn-tg mice, while the level of Triton X-soluble human α-syn was not affected. Furthermore, the number of p-α-syn immunoreactive inclusions was reduced in α-syn-tg mice treated with PLX3397. Microglial depletion also ameliorated neuronal and synaptic degeneration in α-syn-tg mice, thereby resulted partially improving the motor behavioral deficit in α-syn-tg mice. Moreover, we demonstrated that microglia that survived post-PLX3397 treatment (PLX-resistant microglia) have lower expressions of CSF-1R, and microglial transcriptome analysis further elucidated that PLX-resistant microglia have unique morphology and transcriptomic signatures relative to vehicle-treated microglia of both genotypes; these include differences in definitive microglial functions such as their immune response, cell mobility, cell-cell communications, and regulation of neural homeostasis. Therefore, we suggest that microglia play a critical role in the pathogenesis of synucleinopathies, and that modulation of microglial status might be an effective therapeutic strategy for synucleinopathies.

DOI: https://doi.org/10.1016/j.bbi.2024.09.016
J Neuroinflammation. 2024 Sep 19. 21(1): 232

A comprehensive review of AAV-mediated strategies targeting microglia for therapeutic intervention of neurodegenerative diseases.

Livia Zhou, Yafeng Wang, Yiran Xu, Yaodong Zhang, Changlian Zhu.

  Neurodegenerative diseases pose a significant health burden globally, with limited treatment options available. Among the various cell types involved in the pathogenesis of these disorders, microglia, the resident immune cells of the central nervous system, play a pivotal role. Dysregulated microglial activation contributes to neuroinflammation and neuronal damage, making them an attractive target for therapeutic intervention. Adeno-associated virus (AAV) vectors have emerged as powerful tools for delivering therapeutic genes to specific cell types in the central nervous system with remarkable precision and safety. In the current review, we discuss the strategies employed to achieve selective transduction of microglia, including the use of cell-specific promoters, engineered capsids, and microRNA (miRNA) strategies. Additionally, we address the challenges and future directions in the development of AAV-based therapies targeting microglia. Overall, AAV-mediated targeting of microglia holds promise as a novel therapeutic approach for neurodegenerative diseases, offering the potential to modify disease progression and improve patient outcomes.

Keywords:  Adeno-associated virus (AAV); Gene Therapy; Microglia; Microglia Tropism; Neurodegenerative diseases

DOI:  https://doi.org/10.1186/s12974-024-03232-2
Cell Death Dis. 2024 Sep 15. 15(9): 676

SMAC mimetic drives microglia phenotype and glioblastoma immune microenvironment.

Emmanuel Snacel-Fazy, Aurélie Soubéran, Magali Grange, Kevin Joseph, Carole Colin, Philippe Morando, Hervé Luche, Alessandra Pagano, Sophie Brustlein, Franck Debarbieux, Soline Toutain, Carole Siret, Serge A van de Pavert, Geneviève Rougon, Dominique Figarella-Branger, Vidhya Madapusi Ravi, Emeline Tabouret, Aurélie Tchoghandjian.

Tumor-associated macrophages/microglia (TAMs) are highly plastic and heterogeneous immune cells that can be immune-supportive or tumor-supportive depending of the microenvironment. TAMs are the most abundant immune cells in glioblastoma (GB), and play a key role in immunosuppression. Therefore, TAMs reprogramming toward immune-supportive cells is a promising strategy to overcome immunosuppression. By leveraging scRNAseq human GB databases, we identified that Inhibitor of Apoptosis Proteins (IAP) were expressed by TAMs. To investigate their role in TAMs-related immunosuppression, we antagonized IAP using the central nervous system permeant SMAC mimetic GDC-0152 (SMg). On explants and cultured immune cells isolated from human GB samples, SMg modified TAMs activity. We showed that SMg treatment promoted microglia pro-apoptotic and anti-tumoral function via caspase-3 pro-inflammatory cleavage and the inhibition of tumoroids growth. Then we designed a relevant immunogenic mouse GB model to decipher the spatio-temporal densities, distribution, phenotypes and function of TAMs with or without SMg treatment. We used 3D imaging techniques, a transgenic mouse with fluorescent TAM subsets and mass cytometry. We confirmed that SMg promoted microglia activation, antigen-presenting function and tumor infiltration. In addition, we observed a remodeling of blood vessels, a decrease in anti-inflammatory macrophages and an increased level of monocytes and their mo-DC progeny. This remodeling of the TAM landscape is associated with an increase in CD8 T cell density and activation. Altogether, these results demonstrated that SMg drives the immunosuppressive basal microglia toward an active phenotype with pro-apoptotic and anti-tumoral function and modifies the GB immune landscape. This identifies IAP as targets of choice for a potential mechanism-based therapeutic strategy and SMg as a promising molecule for this application.

DOI: https://doi.org/10.1038/s41419-024-07056-z
Acta Neuropathol Commun. 2024 Sep 19. 12(1): 154

Trem2-deficiency aggravates and accelerates age-related myelin degeneration.

Tyler J McCray, Logan M Bedford, Stephanie J Bissel, Bruce T Lamb.

  Aging is the greatest known risk factor for most neurodegenerative diseases. Myelin degeneration is an early pathological indicator of these diseases and a normal part of aging; albeit, to a lesser extent. Despite this, little is known about the contribution of age-related myelin degeneration on neurodegenerative disease. Microglia participate in modulating white matter events from demyelination to remyelination, including regulation of (de)myelination by the microglial innate immune receptor triggering receptor expressed on myeloid cells 2 (TREM2). Here, we demonstrate Trem2-deficiency aggravates and accelerates age-related myelin degeneration in the striatum. We show TREM2 is necessary for remyelination by recruiting reparative glia and mediating signaling that promotes OPC differentiation/maturation. In response to demyelination, TREM2 is required for phagocytosis of large volumes of myelin debris. In addition to lysosomal regulation, we show TREM2 can modify the ER stress response, even prior to overt myelin debris, that prevents lipid accumulation and microglial dysfunction. These data support a role for Trem2-dependent interactions in age-related myelin degeneration and suggest a basis for how early dysfunctional microglia could contribute to disease pathology through insufficent repair, defective phagocytosis, and the ER stress response.

Keywords:  Aging; Microglia; Myelin degeneration; Neurodegeneration; TREM2; White matter

DOI:  https://doi.org/10.1186/s40478-024-01855-3
J Neuroinflammation. 2024 Sep 16. 21(1): 227

Microglia mediate memory dysfunction via excitatory synaptic elimination in a fracture surgery mouse model.

Shuming Li, Huan Liu, Pin Lv, Yu Yao, Liangyu Peng, Tianjiao Xia, Chao Yan, Zhengliang Ma, Zhang-Peng Chen, Chunjie Zhao, Xiaoping Gu.

  Cognitive impairment is a common issue among human patients undergoing surgery, yet the neural mechanism causing this impairment remains unidentified. Surgical procedures often lead to glial cell activation and neuronal hypoexcitability, both of which are known to contribute to postoperative cognitive dysfunction (POCD). However, the role of neuron-glia crosstalk in the pathology of POCD is still unclear. Through integrated transcriptomics and proteomics analyses, we found that the complement cascades and microglial phagocytotic signaling pathways are activated in a mouse model of POCD. Following surgery, there is a significant increase in the presence of complement C3, but not C1q, in conjunction with presynaptic elements. This triggers a reduction in excitatory synapses, a decline in excitatory synaptic transmission, and subsequent memory deficits in the mouse model. By genetically knockout out C3ar1 or inhibiting p-STAT3 signaling, we successfully prevented neuronal hypoexcitability and alleviated cognitive impairment in the mouse model. Therefore, targeting the C3aR and downstream p-STAT3 signaling pathways could serve as potential therapeutic approaches for mitigating POCD.

Keywords:  Complement C3; Microglia engulfment; Postoperative cognitive dysfunction (POCD); STAT3; Synaptic loss

DOI:  https://doi.org/10.1186/s12974-024-03216-2
J Neuroinflammation. 2024 Sep 18. 21(1): 229

The regulation of NFKB1 on CD200R1 expression and their potential roles in Parkinson's disease.

Suzhen Lin, Yimei Shu, Ruinan Shen, Yifan Zhou, Hong Pan, Lu He, Fang Fang, Xue Zhu, Xinrui Wang, Ying Wang, Wei Xu, Jianqing Ding.

   BACKGROUND: Overactivated microglia are a key contributor to Parkinson's disease (PD) by inducing neuroinflammation. CD200R1, a membrane glycoprotein mainly found on microglia, is crucial for maintaining quiescence with its dysregulation linked to microglia's abnormal activation. We and other groups have reported a decline in CD200R1 levels in several neurological disorders including PD. However, the mechanism regulating CD200R1 expression and the specific reasons for its reduction in PD remain largely unexplored. Given the pivotal role of transcription factors in gene expression, this study aimed to elucidate the transcriptional regulation of CD200R1 and its implications in PD.
METHODS: The CD200R1 promoter core region was identified via luciferase assays. Potential transcription factors were predicted using the UCSC ChIP-seq database and JASPAR. NFKB1 binding to the CD200R1 core promoter was substantiated through electrophoretic mobility shift and chromatin immunoprecipitation assays. Knocking-down or overexpressing NFKB1 validated its regulatory effect on CD200R1. Correlation between decreased CD200R1 and deficient NFKB1 was studied using Genotype-Tissue Expression database. The clinical samples of the peripheral blood mononuclear cells were acquired from 44 PD patients (mean age 64.13 ± 9.78, 43.2% male, median Hoehn-Yahr stage 1.77) and 45 controls (mean age 64.70 ± 9.41, 52.1% male). NFKB1 knockout mice were utilized to study the impact of NFKB1 on CD200R1 expression and to assess their roles in PD pathophysiology.
RESULTS: The study identified the CD200R1 core promoter region, located 482 to 146 bp upstream of its translation initiation site, was directly regulated by NFKB1. Significant correlation between NFKB1 and CD200R1 expression was observed in human PMBCs. Both NFKB1 and CD200R1 were significantly decreased in PD patient samples. Furthermore, NFKB1-/- mice exhibited exacerbated microglia activation and dopaminergic neuron loss after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment.
CONCLUSION: Our study identified that NFKB1 served as a direct regulator of CD200R1. Reduced NFKB1 played a critical role in CD200R1 dysregulation and subsequent microglia overactivation in PD. These findings provide evidence that targeting the NFKB1-CD200R1 axis would be a novel therapeutic strategy for PD.

Keywords:  CD200R1; Microglia; NFKB1; Parkinson’s disease; Promoter; Transcription factor

DOI:  https://doi.org/10.1186/s12974-024-03231-3
Glia. 2024 Sep 20.

Microglial morphology aligns with vigilance stage-specific neuronal oscillations in a brain region-dependent manner.

Sarah Steffens, Hilla Mäkinen, Tarja Stenberg, Henna-Kaisa Wigren.

  Microglia, the resident immune cells in the brain, dynamically adapt their morphology based on their functional state. This study explored the relationship between microglial morphology and sleep-wake cycles in mice. Using Iba1 immunostaining to identify microglia, we quantified morphological changes in microglia at different timepoints in multiple brain regions (cortex, hippocampus, basal forebrain, hindbrain, and cerebellum) in B6 male mice using semi-automated 3D structural analysis. Simultaneously, in a separate group, we monitored wake and sleep stage-specific brain activity using EEG/EMG recordings. During natural sleep-wake cycles, we observed increased microglial complexity (enlarged volume, territorial coverage, and ramification) during wakefulness, characterized by high-frequency theta (8-12 Hz) and gamma activity (30-80 Hz). Conversely, during NREM sleep, which is dominated by delta activity (0.5-4 Hz), microglia displayed reduced complexity. Notably, this pattern was absent in brain regions lacking direct functional connections to areas generating vigilance stage-dependent thalamocortical oscillations. We then extended wakefulness to decouple circadian influence from sleep-wake-specific neuronal activity. This procedure attenuated the decrease in microglial complexity observed during natural sleep, suggesting a crucial role for neuronal activity. Subsequent recovery sleep restored microglial features, independent of the time of day (zeitgeber time). These findings reveal a dynamic interplay between vigilance stage-specific thalamocortical activity and microglial morphology across various brain regions. This suggests a potential role for microglia in sleep regulation and warrants further investigation to understand the underlying mechanisms.

Keywords:  EEG; microglia morphology; oscillations; vigilance stages

DOI:  https://doi.org/10.1002/glia.24617
Front Immunol. 2024 ;15 1392077

Microglia in physiological conditions and the importance of understanding their homeostatic functions in the arcuate nucleus.

Mara A Guzmán-Ruíz, Natalí N Guerrero Vargas, Ricardo Jair Ramírez-Carreto, Juan Carlos González-Orozco, Bryan Adair Torres-Hernández, Michelle Valle-Rodríguez, Rosalinda Guevara-Guzmán, Anahí Chavarría.

  Microglia are highly dynamic cells that have been mainly studied under pathological conditions. The present review discusses the possible implication of microglia as modulators of neuronal electrical responses in physiological conditions and hypothesizes how these cells might modulate hypothalamic circuits in health and during obesity. Microglial cells studied under physiological conditions are highly diverse, depending on the developmental stage and brain region. The evidence also suggests that neuronal electrical activity modulates microglial motility to control neuronal excitability. Additionally, we show that the expression of genes associated with neuron-microglia interaction is down-regulated in obese mice compared to control-fed mice, suggesting an alteration in the contact-dependent mechanisms that sustain hypothalamic arcuate-median eminence neuronal function. We also discuss the possible implication of microglial-derived signals for the excitability of hypothalamic neurons during homeostasis and obesity. This review emphasizes the importance of studying the physiological interplay between microglia and neurons to maintain proper neuronal circuit function. It aims to elucidate how disruptions in the normal activities of microglia can adversely affect neuronal health.

Keywords:  arcuate nucleus; hypothalamus; microglia; microglial-neuronal interaction; obesity; physiological function

DOI:  https://doi.org/10.3389/fimmu.2024.1392077
Neurotherapeutics. 2024 Sep 13. pii: S1878-7479(24)00127-2. [Epub ahead of print]21(4): e00440

Hematopoietic stem cell gene therapy to halt neurodegeneration.

Alessandra Biffi.

  Microglia play fundamental roles in multiple pathological primary and secondary processes affecting the central nervous system that ultimately result in neurodegeneration and for this reason they are considered as a key therapeutic target in several neurodegenerative diseases. Microglia-targeted therapies are directed at either restoring or modulating microglia function, to redirect their functional features toward neuroprotection. Among these strategies, hematopoietic stem cell gene therapy have proven to be endowed with a unique potential for replacing diseased microglia with engineered, transplant progeny cells that can integrate and exert relevant beneficial effects in the central nervous system of patients affected by inherited and acquired neurodegenerative conditions.

Keywords:  Gene therapy; Hematopoietic stem cells; Microglia

DOI:  https://doi.org/10.1016/j.neurot.2024.e00440
PLoS Pathog. 2024 Sep 16. 20(9): e1012168

Microglia and macrophages alterations in the CNS during acute SIV infection: A single-cell analysis in rhesus macaques.

Xiaoke Xu, Meng Niu, Benjamin G Lamberty, Katy Emanuel, Shawn Ramachandran, Andrew J Trease, Mehnaz Tabassum, Jeffrey D Lifson, Howard S Fox.

Human Immunodeficiency Virus (HIV) is widely acknowledged for its profound impact on the immune system. Although HIV primarily affects peripheral CD4 T cells, its influence on the central nervous system (CNS) cannot be overlooked. Within the brain, microglia and CNS-associated macrophages (CAMs) serve as the primary targets for HIV and the simian immunodeficiency virus (SIV) in nonhuman primates. This infection can lead to neurological effects and establish a viral reservoir. Given the gaps in our understanding of how these cells respond in vivo to acute CNS infection, we conducted single-cell RNA sequencing (scRNA-seq) on myeloid cells from the brains of three rhesus macaques 12 days after SIV infection, along with three uninfected controls. Our analysis revealed six distinct microglial clusters including homeostatic microglia, preactivated microglia, and activated microglia expressing high levels of inflammatory and disease-related molecules. In response to acute SIV infection, the homeostatic and preactivated microglia population decreased, while the activated and disease-related microglia increased. All microglial clusters exhibited upregulation of MHC class I molecules and interferon-related genes, indicating their crucial roles in defending against SIV during the acute phase. All microglia clusters also upregulated genes linked to cellular senescence. Additionally, we identified two distinct CAM populations: CD14lowCD16hi and CD14hiCD16low CAMs. Interestingly, during acute SIV infection, the dominant CAM population changed to one with an inflammatory phenotype. Specific upregulated genes within one microglia and one macrophage cluster were associated with neurodegenerative pathways, suggesting potential links to neurocognitive disorders. This research sheds light on the intricate interactions between viral infection, innate immune responses, and the CNS, providing valuable insights for future investigations.

DOI: https://doi.org/10.1371/journal.ppat.1012168
J Comp Pathol. 2024 Sep 14. pii: S0021-9975(24)00296-2. [Epub ahead of print]215 10-13

Striking and widespread microglial activation in the brains of Southdown lambs with type II glucocerebrosidosis (neuronopathic Gaucher disease).

John Finnie, Kim Hemsley, Jim Manavis, Helen Beard, John Brealey, Thomas Robertson, Peter Blumbergs.

  Glucocerebrosidosis (termed Gaucher disease in humans) is a lysosomal storage disease, caused by a deficiency of the enzyme glucocerebrosidase, which results in accumulation of the glycolipid substrate glucocerebroside in the macrophage-monocyte system. Three principal forms are recognized in humans, two being neuronopathic and resulting in neurodegeneration. Only two spontaneously arising cases have been described in domestic animals, one in a dog and the other in a flock of Southdown sheep. Since microglial activation is increasingly being recognized as having an important role in the pathogenesis of Gaucher disease and archival brains were available from lambs with type II glucocerebrosidosis, we wanted to determine whether microglia were activated in these brains. Ionized calcium binding adaptor molecule 1 (Iba1), a specific and the most widely expressed immunohistochemical marker of microglial activation, was used. Striking and widely distributed activation of microglia was demonstrated, suggesting that microglia actively participate in the development of neuropathological changes in ovine Gaucher disease. This aspect of Gaucher disease requires further study in any future cases detected in domestic animal species, including the mechanism by which this markedly increased Iba1 expression is related to disease progression.

Keywords:  Gaucher disease; brain; glucocerebrosidosis; microglial activation; pathogenesis; sheep

DOI:  https://doi.org/10.1016/j.jcpa.2024.08.003
Cell Mol Neurobiol. 2024 Sep 17. 44(1): 60

Lactobacilli Cell-Free Supernatants Modulate Inflammation and Oxidative Stress in Human Microglia via NRF2-SOD1 Signaling.

Mariagiovanna Di Chiano, Maria Teresa Rocchetti, Giuseppe Spano, Pasquale Russo, Caterina Allegretta, Giampaolo Milior, Raffaella Maria Gadaleta, Fabio Sallustio, Paola Pontrelli, Loreto Gesualdo, Carlo Avolio, Daniela Fiocco, Anna Gallone.

  Microglia are macrophage cells residing in the brain, where they exert a key role in neuronal protection. Through the gut-brain axis, metabolites produced by gut commensal microbes can influence brain functions, including microglial activity. The nuclear factor erythroid 2-related factor 2 (NRF2) is a key regulator of the oxidative stress response in microglia, controlling the expression of cytoprotective genes. Lactobacilli-derived cell-free supernatants (CFSs) are postbiotics that have shown antioxidant and immunomodulatory effects in several in vitro and in vivo studies. This study aimed to explore the effects of lactobacilli CFSs on modulating microglial responses against oxidative stress and inflammation. HMC3 microglia were exposed to lipopolysaccaride (LPS), as an inflammatory trigger, before and after administration of CFSs from three human gut probiotic species. The NRF2 nuclear protein activation and the expression of NRF2-controlled antioxidant genes were investigated by immunoassay and quantitative RT-PCR, respectively. Furthermore, the level of pro- and anti-inflammatory cytokines was evaluated by immunoassay. All CFSs induced a significant increase of NRF2 nuclear activity in basal conditions and upon inflammation. The transcription of antioxidant genes, namely heme oxygenase 1, superoxide dismutase (SOD), glutathione-S transferase, glutathione peroxidase, and catalase also increased, especially after inflammatory stimulus. Besides, higher SOD1 activity was detected relative to inflamed microglia. In addition, CFSs pre-treatment of microglia attenuated pro-inflammatory TNF-α levels while increasing anti-inflammatory IL-10 levels. These findings confirmed that gut microorganisms' metabolites can play a relevant role in adjuvating the microglia cellular response against neuroinflammation and oxidative stress, which are known to cause neurodegenerative diseases.

Keywords:   Lactobacilli CFS; Cytokines; Gut–brain axis; LPS; NRF2; Postbiotics

DOI:  https://doi.org/10.1007/s10571-024-01494-1
Int J Mol Med. 2024 Nov;pii: 102. [Epub ahead of print]54(5):

Lipid metabolic rewiring in glioma‑associated microglia/macrophages (Review).

Yixuan Ma, Yimin Huang, Feng Hu, Kai Shu.

  Gliomas are the most prevailing brain malignancy in both children and adults. Microglia, which are resident in the central nervous system (CNS), are distributed throughout the brain and serve an important role in the immunity of the CNS. Microglial cells exhibit varying phenotypic and metabolic properties during different stages of glioma development, making them a highly dynamic cell population. In particular, glioma‑associated microglia/macrophages (GAMs) can alter their metabolic characteristics and influence malignancies in response to the signals they receive. The significance of macrophage metabolic reprogramming in tumor growth is becoming increasingly acknowledged in recent years. However, to the best of our knowledge, there is currently a scarcity of data from investigations into the lipid metabolic profiles of microglia/macrophages in the glioma setting. Therefore, the present review aims to provide a thorough review of the role that lipid metabolism serves in tumor‑associated macrophages. In addition, it outlines potential targets for therapy based on lipid metabolism. The present review aims to serve as a reference source for future investigations into GAMs.

Keywords:  cancer; glioma; lipid metabolism; macrophages; microglia

DOI:  https://doi.org/10.3892/ijmm.2024.5426
Heliyon. 2024 Sep 15. 10(17): e36488

Knockout of TNF-α in microglia decreases ferroptosis and convert microglia phenotype after spinal cord injury.

Fanzhuo Zeng, Anqi Chen, Wei Chen, Shuai Cheng, Sen Lin, Rongcheng Mei, Xifan Mei.

  Spinal cord injury (SCI) is a serious and difficult to treat traumatic disease of the central nervous system. Spinal cord injury causes a variety of detrimental effects, including neuroinflammation and ferroptosis, leading to chronic functional impairment and death. Recent studies have shown that microglia/macrophages (M/Ms) at the injury site remain primarily in the pro-inflammatory state, which is detrimental to recovery. However, information on the factors behind pro-inflammatory polarization skew in the injured spinal cord remains unclear. In this study, we found that Tumor Necrosis Factor-α(TNF-α) ablation protected after SCI by suppressing neuroinflammation and ferroptosis. Though using TNF-α knock out mice (TNF-/-), we induced downregulation of TNF-α in M/Ms and further investigated its effect on SCI outcome. In TNF-/- mice, significant behavioral improvements were observed as early as 7 days after injury. We showed that TNF-α inhibition promote injury-mediated M/Ms polarization from pro-inflammatory to anti-inflammatory phenotype in vivo. Furthermore, accumulated iron in M/Ms after SCI increased the expression of TNF-α and the population of M/Ms to pro-inflammatory phenotype. Moreover, zinc supplement reduced the secondary damage caused by iron overload. In conclusion, we found that knock out of TNF-α promotes recovery of motor function after spinal cord injury in mice by inhibiting ferroptosis and promoting the shift of macrophages to an anti-inflammatory phenotype, indicating that there is great potential for this therapy to SCI.

Keywords:  Apoptosis; Ferroptosis; Inflammation; Microglia; Spinal cord injury; TNF-α

DOI:  https://doi.org/10.1016/j.heliyon.2024.e36488
Mater Today Bio. 2024 Oct;28 101230

Rhodium nanozyme mitigates RPE degeneration and preserves vision in age-related macular degeneration via antioxidant and anti-inflammatory mechanisms.

Qian Sun, Yueqi Ni, Kang Wang, Hong Zhang, Jia Liu, Lingjuan Xu, Yin Zhao.

  Age-related macular degeneration (AMD) is the leading cause of blindness among elderly people worldwide. However, there are currently no effective treatments for AMD. Oxidative stress-induced retinal pigment epithelium (RPE) degeneration and the inflammatory response are the main causes of AMD. In this study, a polyethylene glycol (PEG)-coated rhodium nanozyme (PEG-RhZ) with excellent reactive oxygen species (ROS) and reactive nitrogen species (RNS) elimination capability was synthesized for the treatment of AMD. PEG-RhZs protected RPE cell viability and barrier function upon exposure to oxidative stress stimuli. Additionally, microglial migration and iNOS, IL-1β and TNF-α expression were inhibited by PEG-RhZs. In the acute phase of the AMD model, PEG-RhZs significantly alleviated RPE oxidative damage and inhibited microglial activation. In the late stage of the AMD model, PEG-RhZs reduced photoreceptor loss and improved vision impairment. Furthermore, PEG-RhZs showed good biocompatibility and stability both in vitro and in vivo. Collectively, our findings suggest the therapeutic potential of PEG-RhZs for AMD treatment. STATEMENT OF SIGNIFICANCE: AMD is a kind of retinal degenerative disease that poses heavy health burden globally. PEG-RhZs exhibiting robust ROS and RNS scavenging capabilities have shown promise in safeguarding retinal pigment epithelium (RPE) from oxidative stress, suppressing microglia activation and the secretion of pro-inflammatory molecules, mitigating loss of retinal photoreceptor cells, and ameliorating visual impairment. The commendable antioxidant properties, biological safety, and biostability of PEG-RhZs offer valuable insights for the clinical management of AMD.

Keywords:  Inflammation; Microglia; Nanozyme; Oxidative stress; RPE

DOI:  https://doi.org/10.1016/j.mtbio.2024.101230
Eur J Histochem. 2024 Sep 17. 68(3):

Propofol alleviates M1 polarization and neuroinflammation of microglia in a subarachnoid hemorrhage model in vitro, by targeting the miR-140-5p/TREM-1/NF-κB signaling axis.

Lan Wang, Zhenyu Fan, Haijin Wang, Shougui Xiang.

Subarachnoid hemorrhage (SAH) is a devastating stroke caused by ruptured intracranial aneurysms, leading to blood accumulation around the brain. Early brain injury (EBI) within 72 h post-SAH worsens prognosis, primarily due to intense neuroinflammation. Microglia, pivotal in central nervous system defense and repair, undergo M1 to M2 polarization post-SAH, with M1 exacerbating neuroinflammation. Propofol (PPF), an anesthetic with anti-inflammatory properties, shows promise in mitigating neuroinflammation in SAH by modulating microglial activation. It likely acts through microRNAs like miR-140-5p, which attenuates microglial activation and inflammation by targeting TREM-1 and the NF-κB pathway. Understanding these mechanisms could lead to new therapeutic approaches for SAH-related EBI. In this study, BV-2 cell was used to establish in vitro model of SAH, and the expression of miR-140-5p and TREM-1 was detected after modeling. Microglial activity, apoptosis, the inflammatory pathway and response, oxidative damage, and M1/M2 polarization of microglia were evaluated by drug administration or transfection according to experimental groups. Finally, the targeting relationship between miR-140-5p and TREM-1 was verified by dual luciferase reporter assays, and the effect of PPF on the miR-140-5p/TREM-1/NF-κB signaling cascade was evaluated by RT‒qPCR or Western blotting. PPF effectively mitigates apoptosis, neuroinflammation, oxidative damage, and M1 microglial polarization in SAH. In SAH cells, PPF upregulates miR-140-5p and downregulates TREM-1. Mechanistically, PPF boosts miR-140-5p expression, while TREM-1, a downstream target of miR-140-5p, inhibits NF-κB signaling by regulating TREM-1, promoting M1 to M2 microglial polarization. Reduced miR-140-5p or increased TREM-1 counters PPF's therapeutic impact on SAH cells. In conclusion, PPF plays a neuroprotective role in SAH by regulating the miR-140-5p/TREM-1/NF-κB signaling axis to inhibit neuroinflammation and M1 polarization of microglia.

DOI: https://doi.org/10.4081/ejh.2024.4034
Exp Neurol. 2024 Sep 15. pii: S0014-4886(24)00290-5. [Epub ahead of print]382 114964

Gas6/Axl signaling promotes hematoma resolution and motivates protective microglial responses after intracerebral hemorrhage in mice.

Xiang-Hua Ye, Zhi-Ming Xu, Dan Shen, Yu-Jia Jin, Jia-Wen Li, Xu-Hua Xu, Lu-Sha Tong, Feng Gao.

   BACKGROUND: Intracerebral hemorrhage (ICH) stands out as the most fatal subtype of stroke, currently devoid of effective therapy. Recent research underscores the significance of Axl and its ligand growth arrest-specific 6 (Gas6) in normal brain function and a spectrum of neurological disorders, including ICH. This study is designed to delve into the role of Gas6/Axl signaling in facilitating hematoma clearance and neuroinflammation resolution following ICH.
METHODS: Adult male C57BL/6 mice were randomly assigned to sham and ICH groups. ICH was induced by intrastriatal injection of autologous arterial blood. Recombinant mouse Gas6 (rmGas6) was administered intracerebroventricularly 30 min after ICH. Virus-induced knockdown of Axl or R428 (a selective inhibitor of Axl) treatment was administrated before ICH induction to investigate the protective mechanisms. Molecular changes were assessed using western blot, enzyme-linked immunosorbent assay and immunohistochemistry. Coronal brain slices, brain water content and neurobehavioral tests were employed to evaluate histological and neurofunctional outcomes, respectively. Primary glia cultures and erythrophagocytosis assays were applied for mechanistic studies.
RESULTS: The expression of Axl increased at 12 h after ICH, peaking on day 3. Gas6 expression did not remarkably changed until day 3 post-ICH. Early administration of rmGas6 following ICH significantly reduced hematoma volume, mitigated brain edema, and restored neurological function. Both Axl-knockdown and Axl inhibitor treatment abolished the neuroprotection of exogenous Gas6 in ICH. In vitro studies demonstrated that microglia exhibited higher capacity for phagocytosing eryptotic erythrocytes compared to normal erythrocytes, a process reversed by blocking the externalized phosphatidylserine on eryptotic erythrocytes. The erythrophagocytosis by microglia was Axl-mediated and Gas6-dependent. Augmentation of Gas6/Axl signaling attenuated neuroinflammation and drove microglia towards pro-resolving phenotype.
CONCLUSIONS: This study demonstrated the beneficial effects of recombinant Gas6 on hematoma resolution, alleviation of neuroinflammation, and neurofunctional recovery in an animal model of ICH. These effects were primarily mediated by the phagocytotic role of Axl expressed on microglia.

Keywords:  Axl; Gas6; Hematoma; Intracerebral hemorrhage; Microglia; Neuroinflammation

DOI:  https://doi.org/10.1016/j.expneurol.2024.114964
Neuroscience. 2024 Sep 16. pii: S0306-4522(24)00479-2. [Epub ahead of print]

Bulk and single-cell RNA-seq analyses reveals canonical RNA editing associated with microglial homeostasis and its role in sepsis-associated encephalopathy.

Zhi-Yuan Wei, Li-Ping Wang, Di Gao, Lin Zhu, Jun-Fan Wu, Jia Shi, Yu-Ning Li, Xiao-Dan Tang, Yan-Meng Feng, Xu-Bin Pan, Yun-Yun Jin, Yan-Shan Liu, Jian-Huan Chen.

  Previous studies have demonstrated the roles of both microglia homeostasis and RNA editing in sepsis-associated encephalopathy (SAE), yet their relationship remains to be elucidated. In the current study, we analyzed bulk and single-cell RNA-seq (scRNA) datasets containing 107 brain tissues and microglia samples of mice with microglial depletion and repopulation to explore canonical RNA editing associated with microglia homeostasis and evaluated its role in SAE. Analysis of brain RNA-Seq of mice revealed hallmarks of microglial repopulation, including peak expressions of Apobec1 and Apobec3 at Day 5 and dramatically changed B2m RNA editing. Significant time-dependent changes in brain RNA editing during microglial depletion and microglial repopulation was primarily observed in synaptic genes, such as Tbc1d24 and Slc1a2. ScRNA-Seq revealed heterogeneous RNA editing among microglia subpopulations and their distinct changes associated with microglia homeostasis. Moreover, repopulated microglia from LPS-induced septic mice exhibited intensified up-regulation of Apobec1 and Apobec3, with distinct RNA editing responses to LPS, mainly involved in immune-related pathways. The hippocampus from septic mice induced by peritoneal contamination and infection showed upregulated Apobec1 and Apobec3 expression, and altered RNA editing in immune-related genes, such as B2m and Mier1, and nervous-related lncRNA Meg3 and Snhg11, both of which were repressed by microglial depletion. Moreover, expression of complement-related genes, such as C4b and Cd47, were substantially correlated with RNA editing activity in microglia homeostasis and SAE. Our study demonstrates canonical RNA editing associated with microglia homeostasis, and provides new insight into its potential role in SAE.

Keywords:  Brain; Microglial depletion; Repopulation; Sepsis-associated encephalopathy; Single-cell sequencing; canonical RNA editing

DOI:  https://doi.org/10.1016/j.neuroscience.2024.09.027
Chin Clin Oncol. 2024 Aug;13(Suppl 1): AB046

AB046. Dual role of POSTN in maintaining glioblastoma stem cells and immune-suppressive microglia in glioblastoma.

Hao Wang, Youxin Zhou.

   BACKGROUND: Glioblastoma (GBM) is an immunosuppressive, universally lethal cancer driven by GBM stem cells (GSCs). The interplay between GSCs and the immunosuppressive microglia plays crucial roles in promoting malignant growth of GBM, however, the molecular mechanisms underlying this crosstalk are incompletely understood.
METHODS: We performed RNA sequencing to explore the mechanism by which periostin (POSTN) regulates GSCs and microglia. The biological function of POSTN in GBM development was confirmed in vitro and in vivo. Specifically, tumorsphere formation assay, proliferation analysis, migration assays, enzyme-linked immunosorbent assay, immunoblotting, and intracranial mouse model were performed.
RESULTS: We identified POSTN secreted from GSCs promotes GSC self-renewal and tumor growth via activation of the αVβ3/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/β-catenin/FOS like antigen 1 (FOSL1) pathway. In addition to its GSC intrinsic effects, POSTN is able to recruit microglia and upregulate cluster of differentiation 70 (CD70) expression through PI3K/AKT/nuclear factor-kappa B (NFκB) pathway in microglial cells, which in turn promotes the Treg development and functionality, and generates an immunosuppressive tumor microenvironment. Inhibition POSTN disrupts the GSC maintenance, inhibits recruitment of immunosuppressive microglial, reduces Treg development and function, and suppresses GBM growth, suggesting that targeting POSTN may effectively improve GBM treatment.
CONCLUSIONS: In conclusion, our study defined POSTN as a key regulator in mediating the molecular crosstalk between GSCs and immune-suppressive Microglia in the tumor microenvironment in GBM. POSTN activates the PI3K/AKT/β-catenin/FOSL1 pathway in an autocrine manner to promote GSC self-renewal and tumor growth. At the same time, POSTN recruits microglia in a paracrine manner and upregulates the expression of CD70 in microglia through the PI3K/AKT/NFκB pathway, thereby promoting the development and function of Treg and generating an immunosuppressive tumor microenvironment. Our findings indicate that targeting the POSTN gene may be a promising approach to ablating GSCs, breaking the immunosuppressive environment and overcoming treatment resistance in GBM.

Keywords:  Periostin (POSTN); glioblastoma stem cell (GSC); immunosuppressive microenvironment; microglia; regulatory T cell

DOI:  https://doi.org/10.21037/cco-24-ab046
iScience. 2024 Sep 20. 27(9): 110706

Simple and highly specific targeting of resident microglia with adeno-associated virus.

Carolina Serrano, Sergio Cananzi, Tianjin Shen, Lei-Lei Wang, Chun-Li Zhang.

  Microglia, as the immune cells of the central nervous system (CNS), play dynamic roles in both healthy and diseased conditions. The ability to genetically target microglia using viruses is crucial for understanding their functions and advancing microglia-based treatments. We here show that resident microglia can be simply and specifically targeted using adeno-associated virus (AAV) vectors containing a 466-bp DNA fragment from the human IBA1 (hIBA1) promoter. This targeting approach is applicable to both resting and reactive microglia. When combining the short hIBA1 promoter with the target sequence of miR124, up to 98% of transduced cells are identified as microglia. Such a simple and highly specific microglia-targeting strategy may be further optimized for research and therapeutics.

Keywords:  Genetics; Immunology; Molecular Genetics

DOI:  https://doi.org/10.1016/j.isci.2024.110706
Immunopharmacol Immunotoxicol. 2024 Sep 18. 1-10

Galantamine and wedelolactone combined treatment suppresses LPS-induced NLRP3 inflammasome activation in microglial cells.

Dilek Saker, Leman Sencar, Gulfidan Coskun, Tugce Sapmaz Ercakalli, Dervis Mansuri Yilmaz, Sait Polat.

   CONTEXT: Inflammasome NLR family pyrin domain-containing 3 (NLRP3) is associated with neurological disorders. Neuroinflammation can be suppressed by inhibiting NLRP3 inflammasome activation, decreasing neurodegenerative disorder progression. We devised a therapeutic technique that can reduce neuroinflammation induced by microglial activation, avoiding neurodegeneration. We aimed to investigate the mechanisms underlying the pharmacological effects of galantamine and wedelolactone by evaluating the response of the nuclear factor kappa B (NF-κB) signaling pathway and NLRP3 inflammasome in lipopolysaccharide (LPS)-activated N9 microglia.
METHODS: LPS and adenosine triphosphate were used to activate the NLRP3 inflammasome in N9 microglial cells, which were pretreated with galantamine and wedelolactone. Caspase-1, NLRP3, NF-κB, and interleukin (IL)-1β levels were measured using RT-qPCR and immunostaining.
RESULTS: Combined administration of galantamine and wedelolactone rescued microglial cells from LPS-induced cell death. Furthermore, treatment with galantamine and wedelolactone led to the suppression of NF-κB expression. NLRP3, caspase-1, and IL-1β levels were decreased by the combined treatment.
DISCUSSION AND CONCLUSION: The concurrent administration of galantamine and wedelolactone effectively suppresses the production of inflammatory cytokines and NLRP3 inflammasome activation in microglia. This inhibitory effect is likely linked to the NF-κB signaling pathway modulation. Therefore, this combined treatment is a potential therapeutic approach for neuroinflammatory diseases.

Keywords:  Galantamine; NLRP3; inflammasome activation; microglial cell; wedelolactone

DOI:  https://doi.org/10.1080/08923973.2024.2405579
Clin Exp Pharmacol Physiol. 2024 Nov;51(11): e13917

Phillygenin attenuates cell apoptosis and microglia activation in cerebral ischaemia-reperfusion rats through activation of peroxisome proliferator-activated receptor γ.

Chaojun Yan, Guangwei Sun, Changlong Hu, Tao Qiu, Meng Wang, Yongzhong Fan.

  Ischaemic stroke is a common condition that can lead to cerebral ischaemia-reperfusion injury. Phillygenin (PHI), a natural bioactive compound derived from Forsythia suspensa, has been shown to play a crucial role in regulating inflammation across various diseases. However, its specific regulatory effects in ischaemic stroke progression remain unclear. In this study, we established a middle cerebral artery occlusion (MCAO) rat model. Treatment with PHI (50 or 100 mg/kg) significantly reduced cerebral infarction in MCAO rats. PHI treatment also mitigated the increased inflammatory response observed in these rats. Additionally, PHI suppressed microglial activation by reducing iNOS expression, a marker of M1-type polarization of microglia, and attenuated increased brain tissue apoptosis in MCAO rats. Furthermore, PHI's anti-inflammatory effects in MCAO rats were abrogated upon co-administration with GW9662, a peroxisome proliferator-activated receptor γ (PPARγ) inhibitor. In summary, PHI attenuated microglial activation and apoptosis in cerebral ischaemia-reperfusion injury through PPARγ activation, suggesting its potential as a therapeutic agent for mitigating cerebral ischaemia-reperfusion injury.

Keywords:  PPARγ; cerebral ischaemia–reperfusion; microglia activation; phillygenin

DOI:  https://doi.org/10.1111/1440-1681.13917
Mitochondrion. 2024 Sep 12. pii: S1567-7249(24)00124-7. [Epub ahead of print] 101966

Krebs cycle derivatives, dimethyl fumarate and itaconate, control metabolic reprogramming in inflammatory human microglia cell line.

Moris Sangineto, Martina Ciarnelli, Archana Moola, Vidyasagar Naik Bukke, Tommaso Cassano, Rosanna Villani, Antonino D Romano, Giuseppe Di Gioia, Carlo Avolio, Gaetano Serviddio.

  Metabolic reprogramming drives inflammatory activity in macrophages, including microglia, with Krebs cycle (KC) intermediates playing a crucial role as signaling molecules. Here, we show that the bioenergetic profile of LPS-activated human microglialclone 3 cell line (HMC3) is characterized by high levels of glycolysis and mitochondrial (mt) respiration, and the treatment with KC derivatives, namely dimethyl-fumarate (DMF) and itaconate (ITA), almost restores normal metabolism. However, despite comparable bioenergetic and anti-inflammatory effects, the mt hyper-activity was differentially modulated by DMF and ITA. DMF normalized complex I activity, while ITA dampened both complex I and II hyper-activity counteracting oxidative stress more efficiently.

Keywords:  Dimethyl fumarate; Immunometabolism; Itaconate; Krebs cycle; Microglia; Mitochondria

DOI:  https://doi.org/10.1016/j.mito.2024.101966
IBRO Neurosci Rep. 2024 Dec;17 252-262

Cannabinoid type 2 receptor deficiency leads to Aβ-induced cognitive impairment through promoting microglial sensitivity to Aβ in the prefrontal cortex in mice.

Tong Zhang, JiaGuang Sun, Qiang Jiao, ShuaiChen Li, XiangBo Meng, JingPu Shi, Bo Wang.

   Aims: This study is to investigate the effects of Cannabinoid type 2 receptor (CB2R) deficiency on microglia and cognitive function in both Aβ1-42-injected CB2R knockout mice and a transgenic mouse model of Alzheimer's disease (AD) in brain.
Methods: After hippocampal injection with Aβ1-42 oligomers in CB2R knockout mice with and without CB2R agonist treatment and in transgenic APP/PS1 mice with CB2R deletion, the novel object recognition (NOR) and Morris water maze (MWM) tests were performed to assess the animal behavior performance. Immunofluorescence staining was conducted to detect the microglial morphology and activation status. The expression of proinflammation and anti-inflammation cytokines were determined by qRT-PCR.
Results: CB2R deficiency significantly aggravated cognitive impairment in both Aβ1-42-induced and transgenic APP/PS1 animal model in NOR. In Aβ-injected mice lacking CB2R and transgenic APP/PS1 mice with CB2R deletion, microglia in the prefrontal cortex exhibited enhanced immunoreactivity with altered morphology. Furthermore, transformation of activated microglial phenotype in the prefrontal cortex was reduced in Aβ1-42-injected CB2R knockout mice after CB2R agonist treatment. The CB2R deficiency significantly increased the expression of proinflammatory cytokines in the prefrontal cortex, while it was observed in the hippocampus in both Aβ1-42-injected and transgenic APP/PS1 AD mouse model. Furthermore, CB2R deficiency increased concentrations of soluble Aβ 40 in the prefrontal cortex, but did not affect plaques deposition.
Conclusion: CB2R deletion led to enhanced neuroinflammatory responses via direct upregulating microglia activation in the prefrontal cortex during the early symptomatic phase of AD mice. CB2R modulates prefrontal cortical neuroinflammation, which is essential for regulating cognitive functions such as recognition memory at the early stage of AD.

Keywords:  Alzheimer’s disease; Cannabinoid type 2 receptor; Microglia; Neuroinflammation

DOI:  https://doi.org/10.1016/j.ibneur.2024.08.004
Virol J. 2024 Sep 16. 21(1): 219

HSV-1 immune escapes in microglia by down-regulating GM130 to inhibit TLR3-mediated innate immune responses.

Jia Liu, Xiqian Chen, Junxian Liu, Hainan Zhang, Wei Lu.

   BACKGROUND: To investigate the mechanism of Golgi matrix protein 130(GM130) regulating the antiviral immune response of TLR3 after herpes simplex virus type 1(HSV-1) infection of microglia cells. We explored the regulatory effects of berberine on the immune response mediated by GM130 and TLR3.
METHODS: An in vitro model of HSV-1 infection was established by infecting BV2 cells with HSV-1.
RESULTS: Compared to the uninfected group, the Golgi apparatus (GA) fragmentation and GM130 decreased after HSV-1 infection; TLR3 increased at 6 h and began to decrease at 12 h after HSV-1 infection; the secretion of interferon-beta(IFN-β), tumour necrosis factor alpha(TNF-α), and interleukin-6(IL-6) increased after infection. Knockdown of GM130 aggravated fragmentation of the GA and caused TLR3 to further decrease, and the virus titer also increased significantly. GM130 knockdown inhibits the increase in TLR3 and inflammatory factors induced by TLR3 agonists and increases the viral titer. Overexpression of GM130 alleviated fragmentation of the GA induced by HSV-1, partially restored the levels of TLR3, and reduced viral titers. GM130 overexpression reversed the reduction in TLR3 and inflammatory cytokine levels induced by TLR3 inhibitors. Therefore, the decrease in GM130 levels caused by HSV-1 infection leads to increased viral replication by inhibiting TLR3-mediated innate immunity. Berberine can protect the GA and reverse the downregulation of GM130, as well as the downregulation of TLR3 and its downstream factors after HSV-1 infection, reducing the virus titer.
CONCLUSIONS: In microglia, one mechanism of HSV-1 immune escape is disruption of the GM130/TLR3 pathway. Berberine protects the GA and enhances TLR3-mediated antiviral immune responses.

Keywords:  Golgi matrix protein 130; Herpes simplex virus type 1 (HSV-1); Innate immune response; Microglia; Toll-like receptor 3

DOI:  https://doi.org/10.1186/s12985-024-02492-x
J Inflamm Res. 2024 ;17 6277-6295

Nrf2 Deficiency Exacerbates Parkinson's Disease by Aggravating NLRP3 Inflammasome Activation in MPTP-Induced Mouse Models and LPS-Induced BV2 Cells.

Ranran Lu, Xu Zhou, Lijie Zhang, Mengdie Hao, Xinling Yang.

   Background: Parkinson's disease (PD) is a movement disorder characterized by the progressive loss of dopamine neurons. Microglia-mediated neuroinflammation drives disease progression and becomes a critical factor in neuronal degeneration. Recent studies have found that nuclear factor-erythroid 2-related-2 (Nrf2) expression levels are reduced during aging and neurodegenerative diseases, but its regulatory mechanism on microglia-induced neuroinflammation has not been fully elucidated.
Methods: In vivo, we used the intraperitoneal injection of the neurotoxic drug neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to establish an animal model of PD and, at the same time, administered Nrf2 inhibitors ML385 and dimethyl fumarate to regulate Nrf2 protein levels. In vitro, we used si-RNA to knock out the Nrf2 gene to intervene in BV2 cells and used lipopolysaccharide (LPS) to stimulate and induce the cell model.
Results: The study found that inhibition of Nrf2 expression aggravated the motor defects of PD mice, accompanied by a significant loss of dopaminergic neurons in the substantia nigra and striatum of the brain. In addition, after inhibition of Nrf2, the malondialdehyde (MDA) level in the substantia nigra of the midbrain of mice increased, and the levels of superoxide dismutase (SOD) and heme oxygenase-1 (HO-1) decreased, accompanied by the proliferation of microglia and astrocytes. In addition, the activation of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome, the assembly of apoptosis-associated speck-like protein containing a CARD (ASC) protein in microglia, and the release of downstream inflammatory factors caspase-1 and interleukin (IL)-1β, were aggravated. At the cellular level, it was found that knocking out the expression of Nrf2 would aggravate the activation of NLRP3 inflammasomes and the assembly of ASC in LPS-induced BV2 cells.
Conclusion: Inhibited Nrf2 activity can reduce the downstream antioxidant enzyme HO-1 and antioxidant levels, induce NLRP3 inflammasome activation and ASC protein assembly in microglia, and ultimately aggravate PD inflammatory response and dopamine neuron degeneration.

Keywords:  NLRP3 inflammasome; Nrf2; Parkinson’s disease; microglia; oxidative stress

DOI:  https://doi.org/10.2147/JIR.S478683
Life Sci. 2024 Sep 12. pii: S0024-3205(24)00647-7. [Epub ahead of print] 123057

P2Y12-targeted modulation of microglial phenotypes: A novel therapeutic strategy for enhanced axonal regeneration post-spinal cord injury.

Kai Zhang, Runlin Wen, Wanrong Ma, Huaqing Ji, Xinghui He, Zhiquan Yang, Dingyang Liu, Xing Li.

   AIMS: Microglia activation after spinal cord injury (SCI) is a double-edged sword, modulation of the activated microglia populations toward pro-regenerative phenotypes highlights the potential therapeutic implications. P2Y12, a microglia-specific marker, remains underexplored in its capacity to polarize microglial activation populations in SCI repair. We aimed to explore the effects of modulating P2Y12 on microglia function after spinal cord injury, and further on axonal regeneration and motor recovery after spinal cord injury.
MATERIALS AND METHODS: The study employed both in vitro and in vivo models, using BV2 cells and a mouse model of SCI, respectively. Ticagrelor, a P2Y12 antagonist, was administered via a collagen scaffold to ensure stable and sustained release. Transcriptome sequencing analysis, immunofluorescence staining, and Basso Mouse Scale (BMS) scores were used to assess microglial activation, axonal regeneration, and functional recovery.
KEY FINDINGS: Herein, we observed P2Y12+ microglia localized predominantly at the lesion periphery within 3 days post injury (dpi), manifesting a pro-inflammatory phenotype, but not anti-inflammatory phenotype. In vitro investigations revealed that P2Y12 inhibition of the activated microglia curtailed pro-inflammatory differentiation while augmenting anti-inflammatory differentiation.
SIGNIFICANCE: Leveraging this insight, we engineered a collagen scaffold-based delivery system for sustained release of the P2Y12 antagonist, ticagrelor, at the injury site in a mouse complete SCI model. Notably, P2Y12 suppression markedly enhanced axonal regeneration within the injured site and ameliorated lower limb motor functions in SCI mice. Collectively, our findings illuminate P2Y12-targeted microglial modulation as a promising therapeutic approach for SCI.

Keywords:  Collagen scaffold; Microglia; P2Y12; Spinal cord injury; Ticagrelor

DOI:  https://doi.org/10.1016/j.lfs.2024.123057
J Mol Med (Berl). 2024 Sep 20.

Constitutive expression of the deubiquitinating enzyme CYLD does not affect microglia phenotype or function in homeostasis and neuroinflammation.

Eva Schramm, Vanessa Becker, Ilaria Palagi, Melanie Müller, Thomas Rösler, Feyza Durak, Anna Ebering, Khalad Karram, Esther von Stebut, Michael J Schmeisser, Ari Waisman.

  The deubiquitinating enzyme CYLD negatively regulates NF-κB signaling by removing activating ubiquitin chains from several members of the NF-κB pathway. Thereby, CYLD is critical for the maintenance and differentiation of various immune cells. Despite the importance of the NF-κB pathway in microglia regulation, the role of CYLD in microglia has not been investigated so far. In this study, we investigated whether CYLD in microglia can protect against neuroinflammation using a newly generated conditional mouse strain (Rosa26-Cyld-tdTomato) that allows cell type-specific CYLD overexpression. Here, we show that overexpression of CYLD in microglia did not alter microglia numbers or microglia morphology in different brain regions. Additionally, CYLD overexpression did not modify the microglial response to LPS-induced neuroinflammation or the disease severity in experimental autoimmune encephalomyelitis (EAE). Finally, also immune cell infiltration into the CNS during EAE and under steady state conditions remained unaffected by microglial CYLD overexpression. Our findings suggest that CYLD overexpression does not alter microglial function, and thus does not represent a viable therapeutic strategy in neuroinflammatory conditions. This study highlights the complexity of ubiquitin-mediated signaling in neuroinflammation and the need for cell-type-specific investigations. The Rosa26-Cyld-tdTomato mouse model offers a valuable tool for studying CYLD's role across various tissues and cell types. KEY MESSAGES: Novel mouse strain for cell type-specific overexpression of the deubiquitinating enzyme CYLD. CYLD overexpression in microglia did not alter microglia numbers or morphology in the steady state. CYLD overexpression in microglia did not protect mice from LPS-induced neuroinflammation or EAE. CYLD overexpression in microglia did not influence their gene expression during neuroinflammation.

Keywords:  CYLD; Deubiquitinating enzyme; EAE; Microglia; NF-κB; Neuroinflammation

DOI:  https://doi.org/10.1007/s00109-024-02489-7